Up to you.
I think all the buttons in each theme can be edited Maffe by just adding this code snippet to the gtkrc file.
I believe this changes the button corner curvature radius angle and uses the aurora dll engine which calls the style for the widgets.You can try it and see.
menubarstyle = 2 # 0 = flat, 1 = gradient, 2 = sunken
curvature = 6.2
arrowsize = 1 # controls combo_arrow circle size. Diameter set by (11 + 2 * arrowsize)
old_arrowstyle = FALSE #set to TRUE for original circled arrows
animation = TRUE # FALSE = disabled, TRUE = enabled